The present invention concerns a device for capturing the silhouette of an individual, a set of several of these capture devices and a lobby using such a capture device. The invention finds an application in the field of the analysis and recognition of the silhouette of an individual and in particular of an individual passing through a security lobby.
In order to check that only one individual is entering a building, a lobby is provided at the entrance to this building. Such a lobby may comprise a small room with an entry and exit and a uniqueness detection device provided for checking that only one individual is passing through the lobby.
A uniqueness detection device is known, comprising a floor mat consisting of a matrix of sensors and an electronic processing unit connected to the various sensors. The feet of an individual passing through the lobby come to press on the sensors and these various pressure zones, and the processing unit deduces from this the number of feet passing through the lobby and therefore the number of individuals passing simultaneously through the lobby. Such a uniqueness detection device does not give complete satisfaction since it does act make it possible to distinguish when an individual is passing through the lobby carrying another individual on his back. The uniqueness detection device in fact detects a single pair of feet whereas two individuals have passed through the lobby.
In order to resolve this problem, another uniqueness detection device has been developed. This uniqueness detection device comprises an electronic processing unit and a device for capturing the silhouette of the individual passing through the lobby. The silhouette capture device is designed to capture an image of the silhouette of the individual passing through the lobby in order to transfer this image to the processing unit, which analyses it in order to deduce therefrom that only one individual is actually passing through the lobby. A capture device of this type comprises a vertical opaque wall covered with a chequerboard of black and white squares and a camera whose lens is oriented so as to film this chequerboard. When an individual passes between the lens and the chequerboard, the camera captures a control image on which the individual and chequerboard appear. The control image is then transferred to the processing unit, which analyses it in order to be able to check that only one individual has actually passed.
Analysis of the control image may consist for example of subtracting the image of the chequerboard from the control image in order to extract the silhouette of the individual therefrom. The silhouette of an individual alone or the silhouette of an individual who is carrying another are perfectly differentiable and the processing unit is designed to make a distinction between these two silhouettes.
Even if such a device for capturing the silhouette of individuals gives good results, its does not give complete satisfaction.
This is because a uniqueness detection device or a security lobby comprising such a capture device does not, because of the presence of the opaque wall, enable a controller posted outside the uniqueness detection device or security lobby to see inside the latter. In the event of detection of a problem by the processing unit, the controller must then move in order to check the actual presence or not of the incident.
In addition, the presence of opaque walls is prejudicial vis-a-vis persons passing through the uniqueness detection device or security lobby since these persons may have a sense of being shut in.
The document EP-A-0 551 175 discloses a device for detecting a person passing in front of a wall illuminated by IR LEDs, the beams of which are reflected in the wall and are picked up by a camera. The wall is opaque and fabricated from wood or stone and, where the material constituting the wall is not sufficiently reflective for IR, a specific paint is applied to the wall. A person skilled in the art is therefore not led to replace the opaque wall with a transparent wall as the present invention so provides below, since the document of the prior art would lead him to cover such a transparent wall with a non-transparent paint.